Rheology of surfactant solution Nonlinear extension of tread like micelles and shear induced structure

研究了十六烷基三甲基溴化铵（CTAB）和钙酸钠（鼻）水溶液的非线性流变特性，以研究丝状胶束的有限可扩展性和剪切诱导结构。CTAB的浓度固定在0.1 mol l^<-1>， NaSal的浓度变化在0.07 ~ 0.4 mol l^<-1>。对于所有测试解，动态模量用具有单一松弛时间τ的麦克斯韦模型描述。测量了稳态剪切流开始后的剪切应力σ和第一次法向应力差N_1的时间演变。对于低浓度的溶液，当剪切速率γ超过τ^<-1>时，出现应变硬化现象，σ和N_1在一定应变下偏离。在τ^<-1>和γ > γc之间的^处出现了与普通纠缠聚合物溶液类似的应力超调，而在γ > γc处出现了应变硬化。对于弹性固体，有一个简单的关系，即N_1/σ= γ，其中γ为剪切流施加的应变，适用于应变硬化状态下的所有解。应变硬化归因于应变相关剪切模量，并与考虑网络股有限可扩展性的网络理论进行了很好的描述。在非线性流变测量中，我们发现流变数据在很大程度上依赖于锥板夹具的材料。用玻璃锥板夹具测量的应变硬化行为明显减弱。因此，我们研究了玻璃锥板夹具表面处理的效果。我们发现疏水处理对于观察丝状胶束溶液的硬化行为是非常有效的。发现剪切流停止后观察到的剪切诱导结构取决于表面处理。

Nonlinear rheology of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium calicylate (NaSal) were investigated in order to study the finite extensionability of thread-like micelles and the shear induced structure. The concentration of CTAB was fixed at 0.1 mol l^<-1>, and the concentration of NaSal was varied from 0.07 to 0.4 mol l^<-1>. For all test solutions, dynamic moduli were described with the Maxwell model having a single relaxation time, τ. Time evolutions of the shear stress, σ, and the first normal stress difference, N_1, after inception of the steady shear flow were measured. For solutions having low NaSal concentrations, strain-hardening was observed and σ and N_1 diverged at a certain strain when the shear rate, γ, exceeded τ^<-1>. For solutions with high NaSal concentrations, stress overshoot similar to that of ordinary entangled polymer solutions was observed at ^between τ^<-1> and a certain critical rate, γc, while the strain-hardening was observed at γ > γc. A simple relationship for elastic solids, N_1/σ= γ with γbeing the strain imposed by shear flow, held for all the solutions in the strain-hardening regime. The strain-hardening was attributable to the strain dependent shear modulus and well described with the network theory considering finite extensibility of network strands.In nonlinear rheological measurements, we found that the rheological data significantly depend on the material of cone-plate fixture. Strain hardening behavior measured with glassy cone-plate fixtures was remarkably weakened. Therefore, we examined the effect of surface treatments of glassy cone-plate fixtures. We found that hydrophobic treatments is quite effective to observe hardening behavior of the thread-like micelle solutions. Shear induced structure observed after cession of shear flow was found to depend on the surface treatments.